Thread: GPS numbers don't seem right
08-10-2009, 10:33 PM #1
GPS numbers don't seem right
Finally got a chance to gps my ski and was alittle shocked...with everything in my signature the ski was only running 71 mph@ 7500 rpms...does this sound correct and what can I do to get my rpms up...don't know much about prop bending so if anyone knows someone who can do it let me know...If that is the problem of course...Thanks again guys
08-10-2009, 10:37 PM #2
08-10-2009, 10:48 PM #3
Not enough fuel is one problem, unless you're at or above 3000 ft. elevation.
08-10-2009, 11:19 PM #4
Your down 600 rpm from where you need to be... I'm suprised your even running 71 mph I question the prop???
08-10-2009, 11:54 PM #5
Thanks guys...I bought the prop new from jerry untouched...my elevation is 3,825 ...got fuel pressure at 46 right now cause it seems to run best there...tried the 60psi but really smelt like gas when running so turned it down..the other thing is the inside of the hull gets really warm it seems like so was wondering if the 4" intake is taking in a lot of this warm air and maybe should switch to rear intake and invest in the racing thermostat...thanks again
08-11-2009, 12:29 AM #6
With exact same set-up I m seeing 75MPH @8.000 when temps hi-80s, and constant +76MPH when temps low-80s, both at sea-level
You will achieve best top speed at 8.100RPM
70-72 is actually quite normal if you can only turn 7.500...
Your set-up is fine, not sure about the FPR setting though...
Try to find out what what causes the RPM loss: oil overfill, boost leak from/to IC, etc
Sometimes it can be something very simple, few weeks ago I suddenly lost 600 RPM, I changed my spark plugs, RMPs went back instantly to +8.000, maybe you should start there...
08-11-2009, 09:24 AM #7
I would put your stock 38s back in. You dont need the 42s to run the x charger if you have the RRFPR. Then check for boost leaks, slip moment on charger and check your plugs. You are pretty high at 3800 ft. to
08-11-2009, 09:37 AM #8
Your elevation is killing ALOT of power wich also means you need ALOT less fuel for that set-up than most. I would put the stock 38s back in and set your fuel pressure at about 58lb base and depitch or go with a 14/19 to get your r's up. I highly recomend checking A/F to be safe and get the most out of your conditions. You spent all this money on mods and nows not the time to cut corners. The price of the A/F gauge is peanuts compared to running lean and the damage that can cause and also your leaving power on the table if its not dialed in right.
08-11-2009, 11:44 AM #9
put brand new plugs in right before the runs...we are headed out now and gonna try the 38's with 55 lbs of fuel pressure...also gonna try and change the nozzle ring to get rpm's up but afraid I will lose top end but we will see...If I want to have the prop tweaked what should I have done to it??
08-11-2009, 05:15 PM #10
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